AV Nodal Re-Entry Tachycardia
Abnormal circular conduction
occurs near the
AV node
The information on this web page is provided to assist patients undergoing a cardiac electrophysiology study understand the procedure and hopefully answer such questions as:
It is important that you ask you cardiologist prior to the study if there is anything that you do not fully understand.
Your heart is a specialised muscle that pumps blood around your body. It contains four chambers that hold the blood as it moves around the heart. The two upper chambers (called atria) receive blood from the lungs and body, and contract to move blood to the two lower chambers (called ventricles). The ventricles then contract to pump blood back to the lungs and to the rest of the body. Contraction of these chambers is controlled by the heart's electrical system.
In order to maintain efficient pumping of the heart there must be synchronised contraction of the atria and ventricles. Disorders of the heart's electrical system result in a fast, slow or irregular heart beat, and the ability of the heart to pump blood becomes impaired. Symptoms such as dizziness, weakness, blackouts, shortness of breath, palpitations or chest discomfort may occur.
Abnormal circular conduction
occurs near the
AV node
Abnormal electrical impulses
originate from one or more
large areas of the atria.
Abnormal origin of the
electrical impulse from
the ventricles
Abnormal origin of the electrical
impulse from a small area in the
atria other than the SA node.
Abnormal circular conduction
utilising the AV node
and an "accessory pathway"
connecting the atria and
ventricles
(e.g. Wolff-Parkinson-White Syndrome).
An electrophysiology (or "EP") study is a technique used by cardiologists to evaluate and treat abnormalities of the heart's rhythm. The minute electrical impulses (which cause the chambers of the heart to contract), can be measured using special thin wires called electrode catheters.
These can be passed through veins (usually in the groin) to the heart. The electrical signals detected by these catheters are amplified and displayed on a television screen, and are also recorded on a computer. By analysing these recordings during normal, fast, slow or irregular heart activity, the accurate diagnosis of heart rhythm disorders can be made.
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There are other methods of investigating heart rhythm problems, and you may already have undergone some of these. They include electrocardiography (ECG), 24-hour heart monitoring (Holter Monitoring), event monitors (such as the "King of Hearts" monitor), Tilt Table testing and exercise stress testing. While these methods may be helpful, they have limitations. Unless you have symptoms during one of these tests, your diagnosis may remain unclear.
With an EP study, we are able to pinpoint the electrical problem in your heart more accurately compared to the other tests.
During an EP study it is often possible to reproduce your symptoms, at which time the recordings will make the diagnosis. A curative procedure can frequently be administered at the time of the study.
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The EP study is conducted in the Catheter Laboratory.
A cardiologist will perform the test, assisted by a nurse and a technician. You will be awake during the procedure although sedation may be given, particularly if you feel very anxious. The cardiologist/doctor will tell you what is happening as the study progresses, and will want to know if any feelings or sensations you experience during the study are similar to your heart symptoms.
Normal electrical pathway of the heart and positions of the catheters in the heart.
You will lie on a theatre table, which has an X-ray machine above it. You will be covered with sterile drapes and towels and your groin and/or side of your neck and upper chest will be cleansed with an iodine or alcohol solution. The doctor will then insert some local anaesthetic at the sites where catheters are to be inserted. (Figure 2). You may feel some discomfort with this, but this will disappear as soon as the anaesthetic starts to work (usually less than a minute). If you do feel excessive discomfort or any other symptoms during the procedure you should tell the doctor and nurse.
Wires (or "electrode catheters") are then advanced to the heart and positioned using x-ray guidance (Figure 3). It may take an hour or more to position these wires correctly.
After the wires have been positioned, electrical testing of the heart is performed. You may experience palpitations or a sensation of racing heartbeat, as a result of the electrical stimulation or rhythm disturbance. The rhythm can be restored to normal usually with small electrical impulses (which you will not feel), but occasionally with an electric shock. Such shocks are only given if you lose consciousness (so that you will not feel or remember them).
Like any test where doctors insert tubes or wires into the body, EP studies do carry some risk, although this is very low. Possible complications include blood clots, damage to the heart wall, heart valves or blood vessels, bleeding, bruising and infection. If an electrode catheter needs to be inserted from the upper chest or neck there is a very small risk of causing lung collapse. All of these complications are very uncommon and can be treated.
The radiation exposure to you during the study is minimal, and no specific radiation protection is required.
However, you should advise your doctor prior to the study, if there is any chance that you may be pregnant.
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Some heart rhythm disturbances, particularly those arising from the atria (upper chambers) or from circuits involving both the atria and ventricles, can be cured by delivering a high frequency (radiofrequency) electric current, directly to an area of the heart muscle.
A special steerable catheter is positioned in the area pinpointed by the preceding EP study. Electric current is then delivered which results in heating of the heart tissue at the end of the catheter. Heating the tissue destroys the electrical pathway or group of electrical cells responsible for the abnormal heart rhythm. There may be some minor discomfort during current delivery (usually felt as a burning sensation in the chest), and small doses of pain-killing medication is often administered.
The electrical current is given in pulses lasting 30-60 seconds, and a number of pulses may be required. The cardiologist performing the ablation will ask you not to take any deep breaths or move whilst the electrical current is being delivered. After the ablation has been performed you will be observed for a period of time in the catheter laboratory to ensure that the procedure has been successful.
Occasionally during catheter ablation it is possible to damage the heart's normal conducting system (particularly if the abnormal circuit runs close to the normal electrical pathway). Permanent damage to the heart's normal conducting system may result in an excessively slow heartbeat, requiring implantation of a permanent pacemaker.
The overall risk of this complication is approximately one in two hundred. The cardiologist performing the ablation will let you know if there is any higher risk of this complication in your particular case.
One other rare complication that may occur when catheter ablation is performed on the left side of the heart is "clot embolism". A small blood clot can form adjacent to the area of heart tissue that has been ablated. This can be pumped in to the bloodstream where it may occlude blood vessels in various areas of the body. If, for example, the clot travelled through the bloodstream to the brain this could cause a stroke.
To minimise the risk of this complication, patients who undergo ablation on the left side of the heart are given anti-clotting medications intravenously during the study and are usually prescribed aspirin or other anti-clotting drugs for approximately four to six weeks following the procedure.
Other complications include formation of blood clots in the leg, damage to the heart wall or blood vessels, or a partial collapse of one lung. These uncommon complications are easily identified and can be treated. The overall risk of any complication is approximately one in one hundred.
Not all heart rhythm problems can be treated with catheter ablation. If your doctor thinks that this technique could be used in your case he/she will discuss this with you and obtain your consent for this procedure to be performed at the time of your EP study.
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The majority of patients undergoing EP study and/or catheter ablation are admitted for less than one day. Procedures undertaken in the afternoon may require an overnight stay. You will be required to arrive at the hospital, at the time and location advised.
Any drugs that you take to prevent heart rhythm abnormalities should be stopped 2 to 3 days before the procedure, or as advised by your doctor. Please notify us if you are taking warfarin, as this particular drug will need to be ceased prior to your procedure.
Bring pyjamas with you as you can change into these on your return to the ward, following your test. Do not wear unnecessary jewellery or bring money or valuables into hospital.
The nurse in charge of your care will prepare you for the EP study. You will be dressed in a hospital gown. Before you go to the catheter laboratory your consent form will be checked, and your blood pressure, pulse and temperature will be recorded.
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At completion of the procedure the wires are removed from the heart and tubes are removed from the groin. The cardiologist will discuss the results of the test with you. You will then return to your bed where you will be given something to eat and drink.
The catheter insertion site will be regularly inspected, and your pulse and blood pressure will be re-checked.
If the groin approach has been used, it will be necessary for you to lie flat for at least 3 hours to prevent bleeding from the site. You may be kept on a heart monitor for some hours and your doctor may recommend further treatment.
You will be notified of follow up appointments if necessary.
If you have any further questions, please do not hesitate to ask your doctor.
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We would like to ensure that your transition from hospital to home is as smooth as possible.
If you experience any of the following symptoms:
Rest quietly and contact Hollywood Private Hospital on (08)9346-6000 and ask for the Clinical Nurse of the Angiography Suite or the After Hours Clinical Nurse Manager for assistance and advice.